Binder materials are used in many building and construction applications for forming building materials. A binder material useful for this purpose is the binder material known as Portland cement. The Portland cement comprises limestone, CaCO3, which is mixed with silicon oxide, SiO2, and heated in a cement kiln to form cement clinker. The cement clinker is finely ground together with gypsum, CaSO4, to form the final Portland cement. In preparing a building material, Portland cement is mixed with water and an aggregate material, comprising for example sand and/or gravel, to form concrete.
To reduce the cost of the concrete, a portion of the Portland cement could be replaced with ground granulated blast furnace slag, a material obtained from steel making processes and which comprises CaO, SiO2, and Al2O3.
EP 0 029 069 B1 discloses a hydraulic binder composition comprising as its main components fine powder of granulated blast furnace slag and lightly calcined anhydrous gypsum or gypsum hemihydrate. The hydraulic binder composition of EP 0 029 069 B1 has, however, been found to generate a concrete with relatively low mechanical strength.